Comparison of Antioxidant Effectiveness of Lipoic Acid and Dihydrolipoic Acid

The abilities of dihydrolipoic acid (DHLA) to scavenge peroxynitrite (ONOO(-)), galvinoxyl radical, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cation radical (ABTS(+center dot)), and 2,2'-diphenyl-1- picrylhydrazyl radical (DPPH) were higher than those of lipoic acid (LA). The effectiveness of DHLA to protect methyl linoleate against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation was about 2.2-fold higher than that of LA, and DHLA can retard the autoxidation of linoleic acid (LH) in the beta-carotene-bleaching test. DHLA can also trap similar to 0.6 radicals in AAPH-induced oxidation of LH. Moreover, DHLA can scavenge similar to 2.0 radicals in AAPH-induced oxidation of DNAand AAPH-induced hemolysis of erythrocytes, whereas LA can scavenge similar to 1.5 radicals at the same experimental conditions. DHLA can protect erythrocytes against hemin-induced hemolysis, but accelerate the degradation of DNA in the presence of Cu(2+). Therefore, the antioxidant capacity of -SH in DHLA is higher than S-S in LA. (C) 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:216-223, 2011; View this article online at wileyonlinelibrary.com. DOI 10:1002/jbt.20378